Hydraulic torque converters, devices used to change the ratio of torque to speed between the input and output shafts of the converter, revolutionized the automotive and marine propulsion industries by providing hydraulic means to transfer energy from an engine to a drive mechanism, e.g., drive shaft or automatic transmission, while smoothing out engine power pulses. A torque converter, arranged between the engine and the transmission, typically includes three primary components: an impeller, sometimes referred to as a pump, directly connected to the converter's cover and thereby the engine's crankshaft; a turbine, similar in structure to the impeller, however the turbine is connected to the input shaft of the transmission; and, a stator, located between the impeller and turbine, which redirects the flow of hydraulic fluid exiting from the turbine thereby providing additional rotational force to the pump.
Although assembling blades within a torque converter housing, at first glance, may appear trivial, manufacturing constraints and requirements make the task quite difficult. A shell is formed, e.g., typically by stamping, slots are coined into or punched through the shell, and subsequently blades are positioned within the slots in the shell. Traditionally, the blades have been connected to their respective shell by means of welding. It is to be understood that “welding” in this sense is to be broadly construed. “Welding” is intended to include the following:                Direct fusion of the blades to the shell of the turbine by melting and subsequently hardening at their interface;        Connection by means of an intermediate or connecting molten metal as occurs in gas or arc welding using a metal connecting material usually selected from copper, iron and alloys of at least two of iron, copper, tin, zinc, lead, aluminum, silver, cobalt, chromium and nickel, an example of this method is described in U.S. Pat. No. 3,673,659; and,        Connection using plastic material that is usually a cross linked organic plastic such as an epoxy resin, e.g., as described in U.S. Pat. No. 3,817,656.The most common form of welding utilized in constructing torque converters has been brazing.        
It has been suggested that blades might be secured without welding by utilizing mechanical fastening such as tabs on a blade that are inserted into slots or recesses in a turbine shell. Unfortunately, such devices have had serious disadvantages.
A major disadvantage has been that the blade is not held as securely as when welding is used and the blade may thus vibrate to cause noise, part wear and eventual catastrophic failure. Examples of such devices are described in U.S. Pat. Nos. 2,660,957; 3,673,659; and, 5,794,436.
A further major disadvantage has been that there has been an inability, by such mechanical fastening, to obtain a tight fit of the blade with the turbine shell. This results in significant inefficiency since fluid within the turbine can pass between the blade and the turbine body thus failing to direct the kinetic energy in that fluid to the turbine and thereby the input shaft of the transmission. Examples of such devices are described in U.S. Pat. Nos. 2,660,957; 3,673,659; 5,794,436; and, 5,893,704.
Yet another disadvantage is that the mechanical method of attachment may be difficult, complex or time consuming, e.g., rivets or similar connectors are required or the blades and shells are of complex shapes that are difficult or expensive to manufacture and may require complex interlocking arrangements. Examples of such devices are disclosed in U.S. Pat. Nos. 2,660,957; 3,673,659; and, 5,794,436.
U.S. Pat. No. 5,893,704 describes a structure wherein tabs on the blades are described that fit within recesses in the shell of a turbine. An advantage resulting from this structure is that fluid flow between the blades and the shell is restricted thus increasing efficiency. Unfortunately, the increased efficiency is not as great as desired because fluid flow around the blade is only stopped at the location of the tab and fluid can still flow around the vane at other locations because the tab, as a practical matter, cannot be expected to hold the rest of the edge of the blade tightly against the body. This is true at least due to variations in insertable distance of the tab and variations in curvature of the body relative to curvature of the blade. A further serious disadvantage of this structure is that there is no positive holding force applied to the blade since the tab does not pass through the shell of the turbine but merely rests within a depression by friction.
All of the United States Patents described above are incorporated by reference herein as background art.
As can be derived from the variety of devices and methods directed at assembling a torque converter, many means have been contemplated to accomplish the desired end, i.e., retention of a blade within a shell, without the need for expensive welding operations, and thus resulting in lower assembly cost and complexity. Heretofore, tradeoffs between welding techniques and expense for such methods and steps were required. Thus, there has been a long felt need for a torque converter shell having a blade affixed without welding operations, while introducing minimal changes to the overall process of assembly, and maintaining an acceptable level of fluid sealing between the blade and the shell.